Both during and between processing steps fabricating integrated circuit chips, various devices are utilized to handle electronic workpieces. An "electronic workpiece" is defined as any article that is formed during steps of assembling an electrical device. Such articles include semiconductor wafers on which a number of integrated circuit chips are fabricated, the individual chips following dicing of a completed semiconductor wafer, and integrated circuit packages containing one or more chips for attachment to a printed circuit board. Handling tools include vacuum-actuated devices to which a wand tip is removably attached. Air is evacuated from the wand tip to provide a force for picking up workpieces that are brought into contact with the wand tip.
There are advantages to the use of portable vacuum-actuated handling tools, but various factors have made it difficult to manufacture a practical portable vacuum tool that meets the requirements of the electronic industry. These factors include: (1) cost considerations; (2) force requirements; (3) particle generation concerns; and (4) a need for rapid vacuum release. The first two factors are typically tradeoffs. Portable vacuum tools are available, wherein the tool is a two-piece member comprising a base having a vacuum pump and a wand handle having a valve and a wand tip. The base is connected to the wand handle by a hose. The vacuum pressure of such a tool is typically within the range of 5 to 15 inches of Hg. While the available vacuum pressure works adequately in many applications, it is well below the 21 to 26 inches of Hg that is available using in-house vacuum systems at wafer fabrication facilities. Increasing the vacuum capacity within a portable electronic workpiece handling tool has required use of a vacuum pump that is considered cost inefficient by many users.
Regarding particle generation, even minute particulate matter will contaminate a semiconductor wafer. Particulate contaminants on an active area of the wafer will lower the yield, and therefore raise the cost, of the manufacturing process. If the particulate contaminants are excessive, expensive and time consuming cleaning and inspection steps may have to be added to the process. Vacuum pumps in a portable handling tool include bushings which render the pump susceptible to particle generation. Consequently, great care must be taken in the design of vacuum tools for cleanroom operation. Fabrication facilities include in-house vacuum systems in which, unlike portable tools, the vacuum exhaust is released outside of the room in which electronic workpieces are located. For this reason, there is a tendency to use in-house systems and there is a reluctance to use portable handling tools.
The valve on a handling tool plays an important role in the operation of the tool. As noted above, the valve should provide a rapid release of an electronic workpiece. The most common valving mechanism is one in which a user presses a reciprocating button or lever to cause displacement of a valve stem having a cylindrical shape with a circular groove cut into the outside surface. Movement of the button or lever aligns the circular groove with an axial bore through the tool, thereby providing a flow path for evacuation from a wand tip connected to the tool. The cylindrical valve stem is dimensioned to block the axial bore when the circular groove is not aligned with the axial bore. One difficulty with this valving mechanism is that a reduced vacuum pressure remains even after misalignment of the circular groove. Therefore, the release of a lightweight electronic workpiece is slowed. Another difficulty is that such a valving mechanism requires adherence to close tolerances in order to ensure blockage of the axial bore. This often requires a sliding of one part against another, thereby creating another source of particulate contamination.
It is an object of the present invention to provide a generally nonparticulating portable vacuum tool for handling electronic workpieces, wherein the tool is cost-efficient and includes a quick-release mechanism.